FullyCharged cydia tweak brings a “fully charged” indicator in status bar.
Back in the days, iOS used to display a little charging plug right next to your battery icon while your device was connected to a power source and completely charged.
Nowadays, there’s just that lightning bolt that doesn’t turn into a charging plug anymore when it’s done charging leaving you with no indication as to when to disconnect your device.
Note that a battery level of 100% doesn’t automatically mean it’s fully charged; 100% means it’s somewhere between 99% and 100% as it brings it up to a round figure, so having this tweak does make sense even if you display your battery percentage. It turns the lightning bolt into said charging plug when your battery is actually at 100%.
No options to configure.